export interface Script {

​

      /**

       * Whole text of the file as a single string.

       */

      text(): string;

​

      /**

       * History of changes to the file, in a form of objects expected by TypeScript

       * (basically, offset, old length, new length).

       */

      changes(): TypeScript.TextChangeRange[];

​

      /**

       * Used internally, don't ever change.

       */

      _cachedSnapshot: TypeScript.IScriptSnapshot;

    }

  }

​

  class TypeScriptDocumentSnapshot implements TypeScript.IScriptSnapshot {

    version = 0;

    private _text: string = null;

​

    constructor(public scriptData: TypeScriptService.Script) {

      if (this.scriptData.changes)

        this.version = this.scriptData.changes().length;

    }

​

    getText(start: number, end: number): string {

      var text = this._getText();

      var result = text.slice(start, end);

      return result;

    }

​

    getLength(): number {

      var text = this._getText();

      return text.length;

    }

​

    getLineStartPositions(): number[] {

      var text = this._getText();

      var result = TypeScript.TextUtilities.parseLineStarts(text);

      return result;

    }

      var baseVersion = (<any>oldSnapshot).version || 0;

      return this.getTextChangeRangeSinceVersion(baseVersion);

    }

​

    getTextChangeRangeSinceVersion(scriptVersion: number): TypeScript.TextChangeRange {

      if (!this.scriptData.changes)

        return TypeScript.TextChangeRange.unchanged;

​

      // TODO: check that we are not called for changes on old snapshots

​

      var chunk = this.scriptData.changes().slice(scriptVersion);

​

      var result = TypeScript.TextChangeRange.collapseChangesAcrossMultipleVersions(chunk);

      return result;

    }

​

    private _getText() {

      if (!this._text)

        this._text = this.scriptData.text ? this.scriptData.text() : <string><any>this.scriptData;

      return this._text;

    }

  }

}